Optik - International Journal for Light and Electron Optics 227 (2021) 166107 Available online 2 December 2020 0030-4026/© 2020 Elsevier GmbH. All rights reserved. Original research article Design and analysis of a new compact all-optical full-adder based on photonic crystals M.J. Maleki a , A. Mir a, *, M. Soroosh b a Faculty of Engineering, Lorestan University, Khorramabad, Iran b Faculty of Engineering, Department of Electrical Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran A R T I C L E INFO Keywords: Optical devices Optical full-adder Photonic bandgap Photonic crystal Resonant cavity ABSTRACT In this paper, a new structure based on photonic crystals for all-optical full-adder is proposed. The two-dimensional structure includes 28 and 12 Chalcogenide rods along the x and z directions, respectively. This structure consists of three waveguides for guiding the introduced optical signals to the main waveguide. Three resonant cavities are connected to the main waveguide and transmit the optical waves toward two output ports (SUM and CARRY) based on optical in- tensities in the main waveguide. Nonlinear rods in cavities are made of the doped glass with a nonlinear refractive index of 10 14 m 2 /W. The defect radii in resonant cavities are 1.1, 1.04, and 0.98 times of the fundamental rods. The lattice constant of the structure is 461 nm and the area of the device is just 71 μm 2 . The fnite difference time domain and plane wave expansion methods are used to simulate the light propagation and the band diagram. For SUM port, the highest normalized powers for logic 0 and the least normalized powers for logic 1 are equal to 4 % and 84 %, respectively while they are 5 % and 121 % for CARRY port. So, the contrast ratio of SUM and CARRY ports are 13.22 dB and 13.84 dB, respectively. The calculated delay time of the presented adder is just around 390 fs. According to the obtained results, the proposed structure can be used in optical processing applications. 1. Introduction In recent years, due to the increasing demands for fast processing, designing optical devices has become an attractive feld for researchers [1,2]. High-speed and high-security of optical signal processing make the attentions to design all-optical devices such as logic gates [3–5], flters [6,7], demultiplexers [8–10], decoders [11–13], encoders [14–16], fip-fops [17–19], half-adders/subtractors [20–27], analog to digital converters [28–30], and digital to analog converter [31]. High-performance adders play an important role in optical processing applications [32,33] and few structures have been presented for all-optical full-adders [34–38]. Mach-Zehnder interferometer (MZI) has been known as an essential component for the combination of optical signals. Semi- conductor optical amplifer Mach-Zehnder interferometer (SOA-MZI) has widely been used to design optical full-adders [39–42]. These structures require high current density for optical amplifcation, and the footprint is large. Some attempts have been made for designing the plasmonic-based optical full adders [43–46]. Low extinction ratio, sensitivity to phase, and diffculty to control surface plasmonic plasmons are the main challenges of these devices. Recently, a graphene-based plasmonic full-adder has been presented, which gives the high extinction ratio and the small footprint for a wavelength of 13.8 μm [47]. * Corresponding author. E-mail address: mir.a@lu.ac.ir (A. Mir). Contents lists available at ScienceDirect Optik journal homepage: www.elsevier.com/locate/ijleo https://doi.org/10.1016/j.ijleo.2020.166107 Received 4 April 2020; Received in revised form 19 November 2020; Accepted 30 November 2020